CFD simulation and experiments of dynamic parameters in gas–solid fluidized bed

Abstract

Particle and bubble motion plays an important role in determining the hydrodynamic characteristics of a fluidized system. The dynamic parameters of a fluidized bed are reflection of the complex correlation between particle–particle and particle–bubble in a system. A two-dimensional Eulerian–Eulerian model integrating the kinetic theory of granular flow is used to simulate the bubble and linear low density polyethylene (LLDPE) particle dynamic behavior in a gas–solid fluidized bed. The simulated method is validated by pressure fluctuation experiment. The computed vertical turbulent energy spectrum of particles is applied to identify the particle motion intensity and the inhomogeneity of turbulent energy dissipation. The energy spectrum captures the Levy–Kolmogorov law in inertial range at high frequency. Furthermore, the flatness factors of wavelet decomposition coefficients of particle fluctuation velocity are for the first time introduced to analyze the intermittence caused by coherent structures in the flow field. The results show that the intermittence in dissipation range is much stronger than that in energy-containing and inertial range, and reinforces rapidly as the radial distance and the bed height increase. Moreover, the acoustic emission (AE) energy is found to be able to indicate the flow regimes. By combing granular temperature and AE energy, the relationship between the spatial distribution of granular temperature and the flow regimes is established. To get more detail of bubble motion behavior, the power spectrum of voidage fluctuation is analyzed. This work provides valuable insights into the dynamic characteristics and the flow field information of a gas–solid fluidized bed by CFD simulation.